Heterodyne dual-polarization epi-detected CARS microscopy for chemical and topographic imaging of interfaces

Abstract

We present a label-free vibrational microscopy technique recently developed by us, which offers backgroundfree chemically-specific image contrast, shot-noise limited detection, and phase sensitivity enabling topographic imaging of interfaces. The technique features interferometric heterodyne detection of coherent anti-Stokes Raman scattering (CARS) in epi-geometry, as well as multi-modal acquisition of stimulated Raman scattering and forward-emitted CARS intensity in the same instrument. As an important biologically-relevant application, epi-detected heterodyne CARS imaging of individual lipid bilayers is demonstrated. We show that we can resolve a single lipid bilayer, distinct from a double bilayer, and measure the phase of its susceptibility, which provides information about the topography of the bilayer with nanometer resolution. As an additional application example, we show imaging of silicon oil droplets surrounded by an aqueous environment at the glass-water interface, where three different signal generation pathways are distinguished. Our epi-detected heterodyne CARS microscope setup thus paves the way to exciting new experiments pushing the sensitivity and resolution limits of vibrational microscopy to the nanoscale.

Imaging and tracking single plasmonic nanoparticles in 3D background-free with four-wave mixing interferometry

“…Notably, DBS allows us to couple beams of different wavelengths into the microscope when performing other experiments, such as for example coherent antiStokes Raman scattering microscopy . 12 Here, it was used for correlative FWM confocal fluorescence microscopy, as described in section 3.1. The sample can be positioned and moved with respect to the focal volume of the microscope objective by scanning an xyz sample stage with nanometric position precision (MadCityLabs NanoLP200).…”